Inhibition of N-ethylmaleimide of the MgATP-driven proton pump of the chromaffin granules

FEBS Lett. 1982 Nov 22;149(1):71-4. doi: 10.1016/0014-5793(82)81074-0.


The thiol reagent N-ethylmaleimide (NEM) completely inhibits the proton pump activity of the H+-ATPase in chromaffin granule 'ghosts' at concentrations which only partly (approximately 20%) inhibit the Mg2+-dependent ATP hydrolysis. Half-maximal inhibition was obtained at approximately 13 microM NEM as compared to 18 microM for the classical proton channel inhibitor N,N'-dicyclohexylcarbodiimide (DCCD), and the apparent stoichiometry of the inhibitors at complete inhibition was NEM : DCCD congruent to 1 : 2. HIgh concentrations of NEM (greater than 100 microM) induce a dissipation of the transmembrane potential generated by MgATP. These findings establish NEM as a valuable proton channel inhibitor in chromaffin granules and explain the rather complex effect of NEM previously reported for catecholamine accumulation in this organelle.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / metabolism*
  • Adenosine Triphosphate / pharmacology*
  • Adrenal Glands / enzymology
  • Animals
  • Cattle
  • Chromaffin Granules / drug effects
  • Chromaffin Granules / enzymology*
  • Chromaffin System / enzymology*
  • Ethylmaleimide / pharmacology*
  • Hydrogen-Ion Concentration
  • Kinetics
  • Proton-Translocating ATPases


  • Adenosine Triphosphate
  • Adenosine Triphosphatases
  • Proton-Translocating ATPases
  • Ethylmaleimide